Laser has been used not only in industrial devices but also in many medical and dental devices. Generally, each of medical and dental devices using laser includes a laser generator for generating laser, a hand instrument for guiding and then emitting laser toward a desired surgical site, and a passage or tube connecting between the laser generator and the hand instrument for transmitting laser from the laser generator to the hand instrument. Typically, the laser transmitting tube is defined from a flexible optical fiber around which is covered with a flexible protecting tube, allowing the laser to be projected onto a desired surgical site and at a desired angle.
As such, since the laser transmitting tube is made of flexible optical fiber, it can be bent sharply as much as the optical fiber would eventually be stressed to damage. The damage of the transmitting tube may result in that leaked laser burns out a corresponding portion of the outer protecting tube. This fails to ensure that a desired amount of laser would be emitted out of the hand instrument.
To solve this problem, various methods have been proposed for detecting failures of the laser transmitting tube. For example, Japanese Utility Model Publication No. 60-21046 discloses a failure detecting device. In this device, a wire is herically wound along the laser transmitting tube. With the device, once the laser transmitting tube is broken, leaked laser melts a corresponding portion of the wire, which is electrically detected.
Also, Japanese Patent Laid-Open Publication No. 60-60531 discloses another failure detecting device. In this device, a cable made from a plastic fiber is mounted adjacent the laser transmitting tube. The device includes a detector capable of detecting failures of the laser transmitting tube. With the device, once the laser transmitting tube is broken, the leaked laser melts a corresponding portion of the plastic fiber, which is detected by the detector.
Further, Japanese Utility Model Publication No. 58-7365 discloses another failure detecting device. The device includes a photodiode positioned adjacent an outlet of the laser transmitting passage. This allows the device to detect the failures or damages of the laser transmitting passage from a variation of the intensity of the laser emitted out of the outlet.
Furthermore, Japanese Patent Laid-Open Publication NO. 56-40737 discloses another failure detecting device. In this device, an outlet of the laser transmitting passage is applied with a coating capable of increasing an intensity of reflected laser and a detector for detecting the reflected laser. With the device, the detector detects a variation of the intensity of the reflected laser, allowing it to detect failures of the laser transmitting passage.